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07 , 60 hp 4 stroke stalling

M

Mikey N.C.

Advanced Contributor
Have a 60 hp Yamaha. Runs great on muffs , replaced high pressure pump in vast chamber and filter, replaced gas in tank and lines from tank to engine new bulb. Boat in lake runs great for 100 yards then starts stumbling and dies. Crank engine back up and idles fine will idle all day. Full throttle about 100 yards and dies. Any ideas and how do you test crankshaft position sensor?
 
Hi.

There is no crankshaft position sensor. If you mean the throttle position sensor, you have to measure the output voltage. But if it's stumbling and totally stalling out, I would focus more on the fuel system. Why did you replace the high pressure fuel pump?

Does the primer bulb get soft when it stalls?
 
High press. pump in vst chamber wasn't coming on when ing. switch was turned on.
If it's not a cps , what's sensor on port side that has 2 wires and magnet that magnets on out side of flywheel pass? How do injectors know when to fire off ?
 
We're also thinking fuel related problems. I have 44 psi fuel rail reading at idle and 35 psi at full throttle, thinking it my be primary fuel pump issue.
 
44 at idle (assuming the engine has warmed up for a few minutes) seems too high. I would expect closer to 33 at idle after warmup. Maybe the injectors are clogged or the pressure regulator is stuck. I'd lean more toward the injectors being clogged, considering the symptoms. But again, if the bulb is going soft, then that points toward the mechanical fuel pump or a leak in one of the fuel lines.

The sensor near the flywheel is the pulser coil. That provides feedback to the ECM so it can determine the timing.
 
We're rethinking . our pick pump is leaking at gaskets, going to tree off filter between maual pump and vst chamber and read fuel pressure.
 
Definitely fix the leak first, but the fuel pressure should really be measured at the rail. Anywhere else, I'm not sure it will tell you much. The only specs I've seen are for the pressure at the rail. If you fix the leak and the bulb stays hard while the engine runs, I don't think a measurement at the mechanical pump is necessary. All the mechanical pump has to do is keep the VST chamber full.
 
We're thinking that mech. pump is sucking air, I'm going to install clear gas line and pressure gauge between mech. pump and vst chamber if that reading drops dramatically I'll know it from vst chamber back.
 
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